A laser processing machine has been widely used that cuts a workpiece by irradiating the workpiece with a laser beam emitted from a laser oscillator. As the laser oscillator, various oscillators such as a CO2 laser oscillator, a fiber laser oscillator, or a direct diode laser oscillator (DDL oscillator) can be used.
The CO2 laser oscillator is large in size and requires a high cost. On the other hand, the fiber laser oscillator or the DDL oscillator can be reduced in size and requires a low running cost. In addition, the wavelength of a laser beam emitted from the CO2 laser oscillator is about 10 μm. On the other hand, the wavelength of a laser beam emitted from the fiber laser oscillator or the DDL oscillator is about 1 μm. Accordingly, the laser beam emitted from the fiber laser oscillator or the DDL oscillator has a small beam waist and a high power density, and it is suitable for processing a plate material having a thin plate thickness with a high speed.